CAT
CAT@EMIL
The scientific aim at CAT@EMIL is to study the electronic surface/near surface structure of functional materials in the presence of a reactive environment. This includes both gas/solid interfaces (e.g. heterogeneous catalysis) and liquid/solid interfaces (e.g. catalytic water splitting).
Methods
Time-resolved absorption, NEXAFS, EXAFS, Mass Spectrometry, XPS, NAP-XPS, HAXPES
Remote access
depends on experiment - please discuss with Instrument Scientist
| Station data | |
|---|---|
| AP-HE-XPS | |
| Temperature range | 25 - 800 °C |
| Pressure range | 10-12 - 20 mbar; typically 1 mbar |
| Detector | 2D delay line detector (2D DLD) (SURFACE CONCEPT, Mainz) |
| Manipulators | various, exchangeable for optimised sample environments |
| Sample holder compatibility | Homemade concept. For details contact the station manager. |
| Additional equipment | gas analytics
• electron impact mass spectrometer (differentially pumped) • proton-transfer-reaction mass spectrometer (PTR-MS) • (micro) gas chromatograph |
| Applicable at beamline(s) | |
| UE48_EMIL | 80 eV to 2000 eV |
| CPMU17_EMIL | |
Ambient pressure - High Energy XPS (AP-HE-XPS)
The scientific aim at CAT@EMIL is to study the electronic surface/near surface structure of functional materials in the presence of a reactive environment. This includes both gas/solid interfaces (e.g. heterogeneous catalysis) and liquid/solid interfaces (e.g. catalytic water splitting).
Obviously, the understanding of the interaction of a catalyst surface with the reactants plays a key role in a detailed description of catalytic processes. X-ray photoelectron spectroscopy (XPS) is a well-established powerful tool to study in detail the outermost surface of solids but it was traditionally restricted to high vacuum and low pressure conditions. However, recently a methodology based on a differentially pumped electrostatic lens system has gained much interest. Such an instrument is operated by the Fritz-Haber-Institut der MPG (FHI-MPG) at HZB/BESSY II at the ISISS beamline in the low photon energy range. A further developed set-up will be installed at EMIL. The feasibility to investigate buried layers is added by the extension of the kinetic energy range of photo-electrons to up to 7000eV. A very flexible, modular sample environment has been developed that allows to apply AP-XPS to a huge variety of problems.
A sketch of the main components of the AP-HE-XPS instrument and a photo of the complete set-up (courtesy of SPECS GmbH, Berlin) is shown as Fig. 1.
Variable pressure soft X-ray absorption (vP-XAS)
A variable pressure soft X-ray absorption experiment has been constructed by FHI that works in the conversion electron yield detection mode. This set-up allows to measure surface sensitive X-ray absorption spectra in a pressure range between 102 - 105 Pa, i.e. up to atmospheric pressure at temperatures up to 400ºC. This instrument makes it feasible to study heterogeneous catalytic reactions in a broad pressure range and hence allows to link results obtained with AP-XPS and measurments obtained in a catalytic reactor.
A sketch of the set-up is shown in Fig. 2. Similar to the AP-XPS the vP-XAS set-up is rigged in a movable frame which provides the possibility to exchange instruments to be used as endstation at EMIL.
- X-ray photoelectron spectroscopy (XPS) under high vacuum (p=10-10 Pa) and ambient pressure conditions (typically p=100 Pa).
- X-ray aborption spectroscopy (XAS) at pressure up to 1k Pa with NAP-HE-XPS endstation. Installation of variable pressure XAS endstation instead of NAP-HE-XPS system allows NEXAFS in electron yield mode at variable pressure between 1 - 100 kPa at temperatures up to 400ºC.